The present embodiments relate to a device and to a method for recovering a temporal reference in a free-running MRT receive chain.
Magnetic resonance tomography systems are imaging devices that for imaging an examination object orient nuclear spins of the examination object using a strong external magnetic field and excite the nuclear spins to precession around this orientation via a magnetic alternating field. The precession or return of the spins from this excited state into a state with lower energy generates a magnetic alternating field as a response, and this is received by antennae.
With the aid of magnetic gradient fields, a spatial encoding is impressed on the signals, and this subsequently enables assignment of the received signal to a volume element. The received signal is then evaluated, and a three-dimensional imaging of the examination object is provided. Local antennae (e.g., local coils) may be used for receiving the signal, and these are arranged directly on the examination object to achieve a better signal-to-noise ratio.
The resonance frequency of the nuclear spins (e.g., the Larmor frequency) is directly proportional to an external static or quasi-static magnetic field, which is composed of the static magnetic field B0 and the gradient fields.
Frequency and phase of the received magnetic resonance signal are relevant to imaging and are to be precisely adhered to with respect to the pulses emitted for excitation of the precession and among each other in the case of a plurality of parallel receivers. Therefore, all emitted signals are conventionally derived from a central reference clock by frequency division, multiplication, or mixing. The same applies to mixed or sample frequencies on the receive path, so there is a fixed phase reference and frequency reference on the entire signal chain. However, for this, all units are to be supplied with corresponding reference signals, and this leads to thicker and unwieldy cables, for example, in the case of local coils.
Document DE 10 2013 204705 describes a magnetic resonance tomography system having wireless transmission of data from the local coil to an MRT base.
From document DE 10 2011 076918, a transmitting device, a magnetic resonance system, and a method for wireless energy transmission to a local coil system are known.
Document DE 10 2012 210827 discloses a method and a device for determining a communications latency in a magnetic resonance tomography system.